This invention relates to a cap that is used in association with a male electrical plug to prevent insertion thereof into an electrical receptacle by a child. There are a number of prior U.S. patents disclosing caps of this general character such as U.S. Pat. Nos. 2,733,416 to Evalt, 2,654,073 to Katz, 2,664,734 to McEneaney, 2,884,805 to Durrell, 3,416,123 to Husebo, 3,422,389 to Husebo, 3,543,544 to Efston, and 3,781,913 to Liburdi. However, except for the device disclosed in the Liburdi patent, all are more complicated than is necessary to prevent a child from inserting an electrical plug into an outlet. Thus they are too expensive to appeal to this particular market. Furthermore, they are all difficult to use since they require use of a key or some tool to be attached and detached. Also, some of these prior art caps have separable parts making it easier to lose or misplace a part.